Gaussian Gun
This simple gaussian gun is a toy that uses magnets to shoot a ball bearing with surprising velocity.
danger level
- negligible
- moderate
- high
- do not do this
tools
- (None)
materials
- A. Neodymium Magnets
- B. Steel Ball Bearings
- C. Plastic Channel/Track
how-to
- Place the neodymium magnets (available at K&J Magnetics) on the track and place four or five ball bearings in a line touching one side of the magnets.
- Place one more ball bearing on the opposite side of the magnets, far enough away that it isn't pulled toward the magnets.
- When you are ready to fire it, nudge the single ball bearing so it slowing rolls toward the magnets.
- You can also set several of these up in a chain; each one will fire the next with increasing speed.
Feb 5, 2007 | 8:48 am
mike wrote:
How can I get the neodymium magnets? I know there are some in some security systems for clothes, but i aren’t going to pick one.
Feb 5, 2007 | 9:57 am
Dangerously Fun wrote:
@mike:
I buy the magnets online, because normal stores do not have a good selection. There a couple of decent shops online - I prefer K&J Magnetics. Here are the ones I used.
Feb 5, 2007 | 6:45 pm
spurlock wrote:
Does it also work without 4 balls at the end? I mean only 1 projectile at the end and 1 that’s being “launched” from behind.
Feb 5, 2007 | 7:15 pm
Dangerously Fun wrote:
@spurlock
Not really. The extra ball bearings are there to distance the projectile bearing from the magnets. This weakens the magnets’ pull on the projectile, allowing it to fly away more easily. You could try using something else as a spacer but it has to be able to transfer the energy to the projectile efficiently.
Feb 6, 2007 | 2:16 pm
spurlock wrote:
I see, thank you for the very quick reply, I appreciate that.
Feb 8, 2007 | 11:43 am
Anonymous wrote:
i would like to see 10 of those on row :P
Feb 13, 2007 | 7:45 am
Anon wrote:
have you tried to bend a track into a ring?
or maybe use some ring track? multiple groups of balls will create very high ball moving speed!
am I wrong?
Feb 14, 2007 | 9:20 am
Dangerously Fun wrote:
@Anon:
If the track were in a ring the projectiles would slow down on the second time around and they would eventually stop altogether. Each successive bearing being pulled toward the magnets would garner less speed and each one being knocked away would resist more because it is starting closer to the magnets.
Feb 15, 2007 | 10:18 am
KOOKOO wrote:
AWSOME! I made a 5-time sequence, and blew a hole in a cardboard box :) of course, my box was pretty pathetic…
Feb 15, 2007 | 1:42 pm
Euh wrote:
does it work with normal, black magnets?
Feb 15, 2007 | 1:49 pm
Dangerously Fun wrote:
@Euh
It may work, but not nearly as well because standard black (ceramic) magnets are much weaker than neodymium magnets.
Feb 19, 2007 | 2:43 pm
Bill Y wrote:
Awesome! Can someone explain the science behind this?
Feb 19, 2007 | 3:41 pm
Dangerously Fun wrote:
@Billy Y:
I can’t provide a complete, technical explanation but the basic idea is this: when you set up this device, there is potential energy between the magnets and the bearing that is separated from them. When you allow the bearing to roll toward the magnets, that potential energy is converted into kinetic energy. The bearing speeds up very quickly because the strength of the magnetic field is inversely proportional to the square of the distance. The moving bearing is subsequently stopped when it hits the magnets and its kinetic energy is transferred to the last bearing on the other side (the one that can move most easily).
Feb 20, 2007 | 11:57 am
Anonymous wrote:
This works well if you use a round ball shaped magnet. The magnet should be the first ball hit.
To improve instead of rolling a steel ball, roll a second magnetic ball. The double attraction really kicks out the last steel ball.
Nice demo is to show all steel balls, then 1 magnet, and finally two magnets.
Mar 2, 2007 | 1:49 pm
MasterP wrote:
I dont understand where the extra energy comes from toe fire the ball. no energy seems to be used while setting it up. yet the ball leaves the end with more velocity than the trigger ball.
Mar 2, 2007 | 2:05 pm
Dangerously Fun wrote:
@MasterP:
In fact, energy IS stored in the system when you set it up. There is potential energy because the bearing is separated from the magnets.
Mar 2, 2007 | 3:27 pm
Anonymous wrote:
i think that this is a cool science project because you can try in different ways and stuff
Mar 3, 2007 | 8:22 pm
DexX wrote:
I’m not sure about this, but I think the physics works like this…
Have you ever played with a Newton’s Cradle toy? Ball bearings hung from a frame? You lift one ball at the end and drop it, and when it hits the rest of the balls, most of its momentum is transferred to the ball on the end (a little bit is lost to sound energy and probably other things).
This works the same way, but with one important difference - the strong magnet is accelerating the ball to very high speed just before it impacts with the magnets. Now, here’s the trick: just as in Newton’s Cradle, the momentum is transferred down the line to the last ball, but that ball is not being pulled on with anywhere near the power of the original ball, as it is so much further from the magnets. It isn’t moving faster then the original ball (in fact, it’s probably moving more slowly, what ith energy loss through sound, and a smaller but still present backward magnetic pull).
Mar 4, 2007 | 12:23 am
Dangerously Fun wrote:
@Dexx:
Thanks, that’s a great addition to my explanation above.
Mar 14, 2007 | 2:29 pm
hobo wrote:
where can i get a track
Mar 15, 2007 | 3:44 am
Science wins wrote:
hobo: plastic or wooden tracks can be found at hardware or home improvement stores to protect the corners of walls.
Mar 15, 2007 | 6:06 pm
Avitrone wrote:
The energy increases as more sets are placed correct? In theory if you made a quad series insetead of a double, would the energy increase thus giving a faster moving ballbearing?
Mar 16, 2007 | 2:06 pm
yoman wrote:
can you make the track out of legos?
Mar 17, 2007 | 2:00 pm
Anonymous wrote:
Yoman: I think you can made the track from legos but you have to use these glossy, flat blocks.
Mar 18, 2007 | 3:44 pm
Zneon wrote:
This reminds me of that old game Mechwarrior. One had the option of selecting a “Gauss Rifle” as a weapon attachment on your mech. Granted the objects projected were supposed to be huge, but much more believable than your plasma, fusion, etc. gun in many games. Awesome real world application…my mind is racing with ideas!
Mar 19, 2007 | 12:36 pm
Micky wrote:
How big are these magnets?
Mar 19, 2007 | 12:59 pm
Dangerously Fun wrote:
@Micky:
The ones I used were 1/2 inch in diameter and 3/16 inch thick. (I bought them from this site.)
Mar 22, 2007 | 12:01 pm
MacAndroid wrote:
Hmmm DexX is right ! In Newton’s cradle the balls eventually come to rest as the momentum is transferred with less than 100% efficiency each swing. The magnets in the gaussian gun however accelerate the mass of the first ball and transfer the resultant force to the last ball which can escape the reduced magnetic field. The gun has created two pieces of mechanical work by moving the first ball a small distance and the last ball a huge distance. Doing work requires energy and the interesting question is where did that energy come from because energy was used but not depleted as the magnet will have lost none of its strength ? What would be the outcome if there were only one ball attached to the magnets when the first ball was rolled in ? I expect the second ball would not break away. The magnet is expending energy twice by accelerating the first ball and again by holding onto the second one. Again no energy is lost but work has been done !!!
Mar 22, 2007 | 1:10 pm
Dangerously Fun wrote:
@MacAndroid:
You can’t forget about potential energy. (from the separation between the magnets and the bearing)
Mar 22, 2007 | 2:55 pm
Nerd-Chic wrote:
so the energy from the first ball accelerating towards the magnet is transferred to the last ball, and because the resistance of the magnet is less, the last ball keeps accelerating. About right?
Mar 22, 2007 | 6:27 pm
Slant123 wrote:
Nerd-Chic: yes, about right
Mar 26, 2007 | 3:53 pm
The mobsta wrote:
Can i use PVC instead of plastic?
Mar 27, 2007 | 8:53 am
Dangerously Fun wrote:
@The mobsta:
PVC is a type of plastic. Regardless, most non-magnetic materials will work (but avoid aluminum).
Apr 4, 2007 | 6:08 pm
Alan the Great wrote:
I love these things.. I have some magnets on the fridge, and some wall molding for the track, but I don’t seem to have any bearings. Oh well; I’ll go look for some now.
Apr 9, 2007 | 1:49 am
Egon_Freeman wrote:
I believe it to be worth mentioning:
in order to make (very dangerous) “more like weapons-grade” ‘Gauss Gun’ (as the name would imply), the magnet will not be enough. HOWEVER, there are *other* ways of creating a strong magnetic field (even more focused, at that). I’m talking about electromagnets in particular.
Of course, at this point it is clear where the energy required comes from. :-) Theoretically, if one made a circuit that would break as soon as the first ‘projectile’ hit the electromagnet, there would be no ‘backpull’ whatsoever (although in some cases this ‘backpull’ is negligible, in the case of an electromagnet …). Besides, with the ability to control the power ‘injected’ (and thus, the force of the field), many more applications are possible.
It is also worth mentioning, that one could combine the principle behind this project with basic electric coils which would ‘pull’ the projectile further along its path and shut off as it was passing / approaching them. Just a thought (I haven’t tried it out… yet), but - if done correctly - could actually create something that might be eventually banned as an actual gun (or something close). The electronics required for this wouldn’t be cheap, though, and the currents involved might get a bit dangerous, so - watch your step.
Apr 13, 2007 | 9:56 am
Yankinwayz wrote:
Since the magnetic pull is converted to mechanical energy after the trigger bearing strikes the magnent, then couldn’t you use simple glass marbles on the projectile side?
Apr 13, 2007 | 4:45 pm
Jon wrote:
Glass marbles work for this like a fishbowl works for shooting hoops.
Apr 18, 2007 | 10:28 am
TBG wrote:
the concept of a Gauss gun is also used in the RTS game Starcraft (Terran Marines and in Halo for the PC (Gauss Warthogs)
i this kinda like a rail gun?
Apr 21, 2007 | 2:05 am
Anonymous wrote:
No not like a rail gun. gauss gun, gauss: measurement of magnetic strength: gauss gun magnet gun. rail gun uses two rail running parallel with the projectile being just big enough (and electrically conductive) to connect the two rails together so a high voltage, high power few ns burst can flow through energizing the rail to repel the projectile that is in between.
To try to help with some explanation about your energy problem. 1. remember the one energy source I haven’t seen metioned in your equation, you have to push the bearing for anything to start happening. 2. while you all mention how the magnet adds energy but doesn’t change it, what about the magnets pull on the other side of the collision, if you don’t have the correct spacing like mentioned, you either risk the whole line of bearings and magnet moving forward or the lack of the magnet holding a small amount of cohesion to smoothly allow the energy to transfer to the last bearing. now the energy the magnet releases is by adding momentum to the approaching bearing, thereby increasing its inertia, while at the same time holding the bearings onthe other side together bracing for impact of the bearing gathering a few head of steam before it collides with the group. When the bearing collides the energy is going to, it set up right, travel through the group to the last bearing where the magnets ability to hold on is the weakest thereby almost instanly giving the last bearing the remaining inertia after friction,heat and overcoming the magnets pull.
Another point to make here, is someone said that the projectile bearing leaves accelerating. No it does not, it goes to full speed after the energy transfer, and decays or changes the energy recieved into friction loss, gravity, heat, drag (which should be extremely small because it is round.
No you cannot keep this cycle of energy going on and on by making the guide track round. Other forces at play like centrifigal force will make sure that will not work. But you can multi-stage it to keep increasing the inertia of the projectile, but to a point. Sooner or later the collision will be to great for the magnet, and as it pulls on the bearing approaching with so much momentum it shatters to pieces absorbing some of it energy and leaving the other bearings in a loose cofiguration, which in turn will look like an explosion rather than a linear transfer of energy.
Apr 22, 2007 | 8:21 am
the densitist wrote:
i wonder the possibilities of strengthening/fortifying the magnets to increase the chain above say… 50.
maybe an incrementally thicker titanium jacket for the magnets?
you could add some punch to this by using the neodymium magnets and some DC current for a much more powerfull electro-magnet.
im sure this would be nowhere close to 100% effecient… but it seems to me this is something that has incredible potential.
if you could obtain 50% effeciency… im thinking you could propel an object at nearly 50% the speed of the electrical current used to enhance the magnets? is that theoretically possible given the magnets will not break?
Apr 25, 2007 | 2:48 am
physicist wrote:
There is a simple way to explain the behaviour of this apparatus. The magnets produce a magnetic field. Take the single ball bearing and attach it at rest to the magnet. Then pull it off the magnet to a long distance - you had to pull hard yes? and then keep pulling until you are out of range. The amount of energy is force times distance along the line of the track. Theres alot of energy in that first pull away from the magnet. Now: try pulling the other ‘fired’ ball bearing away from the magnet- its further away from the magnets and the field there is much weaker. Its force times distance is much smaller than the first ball. These energies are a potential energy when the balls are at a distance. So when you roll the ball towards the magnet, all of that potential energy is converted into kinetic energy by the time the single ball hits the magnet. Now energy is conserved and the collision is in-elastic and just like in newtons cradle the energy is all transferred to the last ball. However that ball must do work against the magnets to acheive its potential energy as it separates. But we found earlier that the potential energy of the end ball is much less and thus there is lots of kinetic energy left over for it to go wizzing off with. The final kinetic energy is the difference of the two potential energies we measured or felt above. Becuase the field falls away very rapidly in this geometry of objects, the speed is quite high. If we could calculate the field pattern (not too hard for a computer and finite element analysis) we could in princple work out how fast the projectile will go.
Combining several machines in series just adds the potential energy of both machines since the ball arrives with extra kinetic energy from the previous machine. There is an optimum spacing of the machines where the potential energy of attraction is reduced only by as much as the potential energy lost by the first separation - that is - if you place the machines close together, the fired ball has not spent all of its energy to escape the magnet before getting attracted to the second machine and therefore there is slightly more kinetic energy from the first machine available. Also by making the machines closer you decrease the potential energy of the attraction. The is a point where these effects balance and the kinetic energy is maximised, although its rather a small gain on a resonable separtion.
The argument above assumes that the magnets and other balls stay put. This isnt exactly true, but their combined mass is enough to make the above argument reasonably accurate. In this regard the setup isnt like newtons cradle. In newtons cradle there are forces on the frame and strings that balance the symmetry of the system and thus the inner balls really do stand still. In this machine there is a slight recoil. This is why you cant cause this effect just with a ball and a magnet. The magnet does ping off because it moves towards the ball as the come together such that the total kinetic energy is exactly zero and they just go snap together.
K.
Apr 25, 2007 | 2:32 pm
Anonymous wrote:
and you call THAT simple?
Apr 25, 2007 | 2:34 pm
pseudonym wrote:
I intend to try this on a MUCH larger scale.IF I live,I’ll send the results
May 19, 2007 | 12:44 am
timmstter wrote:
ok so what if u put another set on those on the other end? what if put 10 in a row? that would bust through a wall, if the magnets dont break
Jun 3, 2007 | 3:27 pm
zaphod wrote:
If you are having trouble figuring where the energy comes from, think of the magnets as a reverse spring. you load it when you take the first ball away after the shot.
Jun 5, 2007 | 10:42 am
BTH wrote:
Can’t have a circular track. Every time a bearing is launched, you lose a bearing from the launch side of the magnet. So every launch shortens the luanch side and lengthens the receiving side. It might go two or three cycles but WILL slow down to a stop!
Jun 15, 2007 | 8:03 am
Umair wrote:
Will the speed of the first rolling ball have any effect on the overall speed of the last ball. If the speed is more will the last ball move out with higher velocity
Jun 27, 2007 | 5:26 pm
panda wrote:
i am going to do a science fair project with this
but, what thing i can prove with this?
Jul 5, 2007 | 4:02 am
Moo wrote:
I think approximates would be fine. I love the lego idea - the only problem is getting a ball bearing that fits perfectly in the channel.
Is there any backlash - if it were handheld would it damage your wrist in any way?
Jul 11, 2007 | 5:45 pm
xian wrote:
i’m an electrical engineer and in college we all had to design a senior project. one kid built a “nail cannon” in consisted of a fiberglass arrow shaft that was hollow, the projectile was a nail shaped object made of metal (not sure what it was probably iron, neodymium would have been interesting to see ). There were 3 largish magnetic coils around the shaft spaced along the length of it, along with 3 photo gates to trip when the nail was near the next coil. A micro controller watched the photo gates and fired the 3 successive coils at the proper times.
the power supply was a 1 farad capacitor bank (for those that don’t know, that is ALOT of power, thousands of amps can be discharged in well under a second, the main feed to your house is only 120amp, less than 1 amp can stop your heart) It took roughly 10 minutes to charge the cap bank, after the nail was fired the micro tripped a circuit that consisted of 3 60watt light bulbs that burnt off the power from the magnetic field back current from when the coils shut down, they stayed lit for a good 15seconds or so after the firing.
in the demonstration i watched he managed several hundred meters per second velocity, enough during the firing to embed the nail into a 1 inch thick brick of lexan (bullet proof glass).
very cool to watch, the story of him trying to get it on a plane was equally entertaining.
-xian
Oct 23, 2007 | 4:18 pm
greg wrote:
does anyone know how big the magnets and ball bearings have to be. The track size would be very helpful. Oh and also can anyone tell me were to get a plastic track such as the one shown?
Oct 29, 2007 | 4:04 am
Dangerously Fun wrote:
@greg:
My magnets were 1/2 inch in diameter and 3/16 inch thick. The ball bearings were also 1/2 inch in diameter. The track was 12 inches long. None of the dimensions are really critical, it should work in many configurations.
Nov 1, 2007 | 11:52 am
Mike wrote:
Here’s a way of explaining it through an analogy…. gravity. Say you’re a circus performer, and there’s a see-saw with a whole lot of metal balls balanced one on top of another right above the “down” end. If you jump from a very high spot, you will accelerate to a high speed, and you will hit the seesaw really hard, causing the other end to hit the column of metal balls on the other side. The top ball (assuming that the column is JUST the right height to just get one quick hit instead of a push) will fly off pretty fast, even though the initial jump off of a diving board was not very fast; gravity provided all of the energy involved. Where did the energy go? Well, you now have to climb the ladder back to the diving board to do it again, which makes it non-repeatable. Keep in mind that in the actual “Gauss Gun”, there is initially no balls on the receiving side of the magnet, while there are five on the firing side. After it has been fired, the receiving side has one ball stuck to it, and I doubt it would even fire again. If it did, the firing would be VERY weak, since there is no fast acceleration near the end.
Nov 3, 2007 | 8:26 pm
Physics Guy wrote:
While I’m no genius, I believe I may be able to help here. The Law of Conservation of Momentum states that “the momentum of a system must always equal the original momentum”. THe ball that is being pulled towards the magnet, does so because the magnet exerts a force on the ball. That force gives the ball velocity ( F=MA velocity is related to aceleration) Also; Momentum = mass x velocity. Because of the low of conservation of momentum, and taking into account all of the balls have the same mass. The velocity with which the ball struck the magnet is “close” to the velocity of the ball. But, because the marble still pulls on the ball as it is being “shot”, the velocity is noticably lower. I have built both a solid magnet version of this, and an electromagnetic Gauss Gun (a.k.a. Coil Gun).
Nov 10, 2007 | 10:58 pm
Simplizer wrote:
Good project. Wanting to try it, I made a mini version using 5 copperclad steel BBs and a 1/8″ X 1/8″ magnet from a little refridgerator figure. I used a note card bent into an “M” shape for a track. Works well.
Nov 28, 2007 | 7:01 am
Gualdo wrote:
The issue on the momentum conservation is clear, as the velocity of the trigger ball when impinges the magnet is similar (actually a bit lower due to losses) than the velocity of the fired ball. The issue of energy conservation has not been so clearly stated. The problem is the following: at the very first begining, the trigger ball has a low velocity; at the end, the fired ball has a high velocity. Why? Because there is an energy conversion: magnetic energy is converted into mechanical energy. The difference between the initial and final configurations is that in the former one has 5 balls on one side of the magnet, and in the latter one has 4 balls on one side and 1 ball on the other side -very close to the magnet. The density of magnetic energy is proportional to the vectors B and H, which have opposite senses within the ferromagnetic balls (so this magnetic energy is negative). In the final configuration, and since the trigger ball is close to the magnet, the magnetic energy is lower (i.e. more negative) than in the initial configuration, and it’s this magnetic energy difference (minus the low kinetic energy of the trigger ball far from the magnet) that is converted into mechanical energy of the fired ball.
T(trigger ball)+E_M(initial conf)=T(fired ball)+E_M(final config).
Since E_M(final config)T(trigger ball).
Dec 6, 2007 | 7:29 pm
Toast_recon wrote:
I know this has all been answered, but I will submit this before I read them so I can test my physics skillz(Sorry). The energy to fire the ball will eventually have come from the energy it took to separate the ball from the magnet. That way, when you took off the ball bearings to set up again, you “stored” that much energy into the ball. Like if you were to take off from a planet, and then go back down. The energy to go down came from the energy it took to go up.
Jan 16, 2008 | 6:30 pm
nobody wrote:
I tried putting all of the materials in a tube (like anonymous suggested) and it was totally awesome!! the balls got less drag and they shot out faster!!
Feb 24, 2008 | 3:23 am
AnonymousMuggle wrote:
After skimming all the replies I noticed the increased speed question didn’t seem to be answered clearly enough. The conservation of energy and momentum answers were very good tho.
It’s not obvious due to the short distance traveled, but it is simply this: Before impact, the trigger bearing accelerates very quickly and is actually going very fast upon impact.
I thought the increased speed was due to the sum of the momentums of the trigger + the magnets & bearings, but it’s not. You have a single trigger/bullet + the same number of bearings & magnets isolated before & after the impact event.
Mar 3, 2008 | 12:35 pm
robar71 wrote:
Has anyone tried a “donut” magnet? That is a larger magnet with hole the size of the bearings in the center, wich was filled with high impact plastic or rubber? My idea is that the magnet would still atract the bearing but the plastic/rubber material would take the brunt of the impact force. This would prevent the solid state magnet from shatering under impact. I beleave that there would be some loss of acceleration due to the imperfect magnet, but how much? For example lets say we use a 12″ diamiter magnet with a 1/4″ hole. Insert a “plastic” tube prefilled with the plastic impact target, projectile and striker bearings. If it worked you could rapidly load new tubes by sliding old ones out and new ones in.
Mar 9, 2008 | 5:38 pm
peanut wrote:
robar71: the donut magnet wouldnt work because the rubber coating would absorb most of the inertia the ball got.
Mar 19, 2008 | 12:49 pm
The Prof wrote:
Expanding on a couple of answers above.
As the trigger ball moves towards the magnets, it is moving from outside the field, zero potential, to a lower (and negative) potential and is therefore losing potential energy which is transferred to kinetic energy. If we ignore friction and assume an elastic collision then all of this kinetic energy is transferred to the bullet ball. Some of this energy is used to escape from the field, the rest remains as kinetic energy in the ball propelling it forward at high speed. This only works because the bullet starts at a higher potential than the potential at which the trigger ball finishes.
No one above has adequately explained how momentum is conserved. There is considerable recoil in the system.
Mass trigger x Velocity trigger = Mass bullet x Velocity bullet + Mass ’system’ x Velocity ’system’. Note that the ’systems’ velocity is negative in this example.
Hope that helps with your science fairs…
Mar 23, 2008 | 9:29 pm
PS wrote:
Regarding the donut shaped magnet: This *will* work, if you don’t use a plastic or rubber core, but simple *steel*.
You can even buy tube-shaped magnets - or *very carefully* drill a hole through a regular neodymium magnet, but beware: it has a consistency like porcellaine; if you’ve never drilled a hole through glasslike substances, you better forget it - and insert a steel rod into it. If you want to go the extra mile, wrap the steel rod into a thin rubbery substance or paint it with rubber glue to prevent stray kinetic energy shattering the magnet around it. Also don’t make the fit too tight, because the rod will get bulged with increasing velocities (see below).
Then you should be able to put many sets in a row and trigger it. Since it wouldn’t be the fairly fragile neodymium magnet that would take the brunt of the respective trigger bearings’ impact, but the steel core inside the magnet, you should be able to achieve truly impressive velocities.
The only boundary to that would - strangely enough - be the velocity of sound in steel, approximately 3.27 miles per second.
Transport of kinetic energy in the steel doesn’t happen instantaneously, but with the speed of sound in steel. I don’t say that the eventually fired bearing can go that fast; that velocity is important for the steel rod inside the magnet. If the velocity of an intermediate bearing will come close to that speed, the steel rod can’t possibly transport the kinetic energy onward fast enough, and so will be deformed at front at impact (as will be the bearing transporting the kinetic impulse towards it).
My estimation is that this will happen way sooner than the aforementioned velocity, but that is for others to check out. ;-)
Further improvements to that could be not to use steel rods but titanium rods farther down the line; to securely fix the magnets in place (you only want forward movement, and the magnets want to move backwards at the time of impact); and not to use several ball bearings behind the magnet but a long shaped metal object, because the ball bearings’ only right to exist (except the last one) is to transport the kinetic impulse out of the magnet’s magnetic field, and you lose energy between each junction; if I would go with my guts I would at first try to shape it like a teardrop: solid kinetic energy receiving area and almost pointed emitting area; but that also would have to to be tested. - Hm… - Come to think of it, forget about the shaped object, just let the steel or titanium cores protrude a few inches out of the magnets’ rear sides and place a single bearing (or whatever) right on the rods’ rear sides. - Wow! ;)
At last position the magnet-rod-bearing sets at such a distance that the attached bearing already strongly feels the pull of the subsequent set. That way you reduce loss of kinetic energy due to friction on the track, too, and avoid the bearing having to escape the last set’s magnetic potential and therefore decelerate, just to accelerate a split second afterwards again towards the next magnet. The gain from that is marginal, because you weaken the potential decline between sets a bit, but more than make up for it due to avoidance of friction. You also wind up with a shorter device and shorter trigger delay. :)
I haven’t really thought this all perfectly through, I just thought I’d leave a quick comment, and got a bit into it. Spur of the moment. ;-} There are probably more ways to improve the Gaussian gun, but it’s late, I’m writing for almost an hour by now, I’m got getting paid for it, and so will leave some finer points to the military to figure out. ;-D (But if they want to hire me, that’s okay, too. ;) )
For those who still don’t understand the basic principle of the Gaussian gun: The whole point is transporting the vectored kinetic energy produced by the magnet out of its magnetic field and use it outside the field. That’s it.
(And btw: I can’t do any testing, I live in Germany, a country where a device that can stamp holes through walls is heavily frowned upon. ;-D )
cu
P
Mar 24, 2008 | 12:14 pm
PS wrote:
You know how it is… lying in bed and ruminating… and writing that was the last thing I did before going to bed… So I saw that I missed an obvious improvement. :)
To reduce the strain on the intermediate magnet-rod-bearing sets it could be advantageous to increase the size and weight of the interjacent sets (or parts of them) and abruptly scale down again towards the end. You still would have to replace the last set or sets fairly frequently, but the intermediate sets would last much longer as they would be sturdier, and the intermediate speed wouldn’t reach the scope of destructive velocities while still being able to transport more and more kinetic energy.
A mixed blessing, granted. Although the device would get heavier and more massive, you would eliminate the weight of the spare parts, which should make a net gain in overall weight to haul around. ;)
Mar 31, 2008 | 11:55 am
Kiddy wrote:
I´d like to react on the post of PS. It sounds like a really neat idea to see how fast you can get those tiny balls by such a simple mechanism. I´ve been thinking about all this though, and i don´t think you´d get at the amazing levels you mentionned. Thinking about a falling guy that´s just about to open his parachute. His speed will decrease till the gravity and friction are equal.
I think the same goes for this mechanism — the magnets will pull the ball, but friction keeps the speed stable. Therefore the next ball will have no longer a speed increase compared to that first ball. Thus: You can reach really nice speeds, but it will never get really extreme.
Mar 31, 2008 | 11:58 am
Kiddy wrote:
Silly me. Using vacuum would simply get rid of this -_-
Apr 8, 2008 | 1:42 pm
Mr. Cakes wrote:
Could this be done using a series of electromagnets instead? That (I believe) would solve the problem of the neodymium magnets shattering/breaking if too many stages are used…
Apr 10, 2008 | 11:08 am
Kiddy wrote:
Sounds very plausible. You WILL have to find a way to shut the electromagnet off immediately at the excact moment the ball goes trough the middle of the electromagnet, which might prove to be a problem at higher speeds.
Apr 13, 2008 | 6:06 pm
super gauss wrote:
If you make this with the magnits below the track with a fized peice of steel on the track above the magnets, you dont break the magnets. in this way I have fired a 1/4 inch stell bearing thought a sheet of 12 mil plywood. To give you an idea thats more force than a 22 caliper rifle.
May 10, 2008 | 6:29 am
Gmod Marto wrote:
Gauss gun can be found in Half-Life 2. The jeep has a gauss rifle on the front right.
May 14, 2008 | 7:21 pm
mechanics wrote:
conservation of energy & conservation of momentum.
potential energy, Ep, created by separating ‘trigger ball’ from magnet.
potential energy converted to kinetic energy, Ek, this is done by the magnetic force on the magnet.
Ep = Ek
conservation of momentum, mass * velocity of trigger ball = mass * velocity of released ball (it’s close enough — but as there is usually a bit of recoil, it makes the released ball go a bit faster).
if balls are of the same mass then the released ball will be travelling roughly the same speed as the trigger ball on impact. a little bit more due to the recoil on the magnet.
a cheep trick is to use a smaller ball bearing as the released ball, and have a larger one as the trigger ball. (makes fired ball go a little bit faster)
May 15, 2008 | 5:54 pm
PS wrote:
@Kiddy: You’re absolutely right, you could eliminate the air friction by placing the intermediate magnet sets in a long vacuum chamber. Makes reloading a bitch, though. ;) Unless you put small electric driven levers next to the track that pull the bearings back in start position. (Complexity is rising… *g*)
´
@Mr. Cakes: Sure, electromagnets will work. That contraption would go under another name, then. It would be called an electromagnet rail gun. The military are already heavily experimenting with that concept and have reached some amazing results. There were some rumors of a ship mounted device (because of size and recoil). The problem there was very probably the power supply. Those electromagnets would need a tremendous amount of electrical power, pre-stored in huge capacitors.
Using capacitors also eliminates the need for switching the electromagnets off. The two remaining problems you face anyway.
First problem: You have to demagnetise the electromagnet very fast after the projectile passed through the magnet coil. A magnet field stores magnetic energy “long after” you pulled the plug, it doesn’t just collapse, it “bleeds out” fast, but not instantaniously. Energy has to go somewhere, it doesn’t just vanish. ;) You accomplish that usually by shorting the contacts to the ground or burn the energy off e.g. in light bulbs (only works in small dimensions; I don’t know how the military do it ;) ).
And your second problem is obviously *timing*. You have to trigger every electromagnet coil at the perfect time to achieve maximum acceleration. A truly hard task to accomplish. Usually done with light barriers, fast relays and testing, testing, testing. - The potential of the rail gun is far greater than the Gauss gun, but definitely it is not a weekend project you would find in Make magazine.
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@super gauss: Yepp, same principle as with tube-shaped magnets with steel rods in them, keep the magnets close to the track so that they can do their magic, but keep them out of harm’s way. It would be interesting to know how many sets you placed in a row to achieve your stated result. Sounds pretty impressive.
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@mechanics: Your formula is correct, but that bit about the recoil is not, I would think. I can’t fully follow your train of thought, but in general recoil is bad for the final velocity, not good. It doesn’t add to the forward speed. (As said, as I see it.) The rest of your post I agree to fully.
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One more thought on the subject to further improve the Gauss gun: Malleable iron dampens a magnet field. So put a disk of iron with a hole in it on the protruding steel rod, effectively reducing the backpull of the just triggered magnet on the rolling bearing ball.
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cu
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May 17, 2008 | 5:37 pm
George wrote:
I’ve been skiming through the comments and I noticed some people were interested in building a larger version of this. I infact spent about 50 bucks last summer to build a bigger one and it didn’t work well at all.
let me repear:
DO NOT TRY TO BUILD A LARGER VERSION!
while the bearing flew fast, it doesn’t even begin to compare with what you can do by throwing with your hand. Infact, at best it’s like a light toss. Trust me, I tried EVERYTHING to fix it, it just doesn’t work on a large scale
May 20, 2008 | 9:51 am
all about fun with agun! wrote:
tried it loved it.if i put a charge at the start or if i shot the first ball bear with my soon new 2 be paint ball gun how much energy whould i get.eg anough t0 stop any 1 robing my ganja plants. im from uk and theres alot of crack/smack heads on the raise/rob any and every hour of the day!!!!!!!!!!!!!
May 21, 2008 | 12:59 am
Ronnie wrote:
i am a student of +2 & living in India and i just cant find Neodymium Magnets here. can i use powerful magnets instead???? i want to make a science project out of it.
May 26, 2008 | 7:56 am
Pete wrote:
@George:
Just letting you know, this isn’t meant to be a weapon, just an interesting device, so speed doesn’t really matter. As the old saying goes, “When a cow dances, you aren’t amazed that the cow dances good, just that it dances at all!” Speaking of speed, though, the Navy is making Gaussian Guns for battleships by the year 2020. They have a range of 200 miles, and can cover that distance in 6 minutes. For the un-mathematical people, that’s 2000 mph! They are 33% faster than Tomahawk missiles, cost only $1,000 per shot (seems like alot, but Tomahawks cost over $1,000,000 per shot), require much less planning (think of one of the old “Plug - and - play” computers), and pack the same punch, even without explosives! It has electromagnets to speed it up. The magnets are so powerful, they use up 64 megajoules per shot! The Navy has already created an 8 megajoule version that they fired January 17, 2007.
Jun 29, 2008 | 11:28 pm
science guy wrote:
which magnet should i get from kng magnets
Jun 29, 2008 | 11:38 pm
science guy wrote:
there are soooooooooooo many
Jul 1, 2008 | 12:50 pm
millar wrote:
so, i happened to think up a theory for an electromagnetic nail gun when i was bored, and after a little research, I realised i had stumbledon the theory for a “gausse cannon” i might try to build one as i have the schematics if anyone is interested.
the basic theory is to use about 10 coiled electromagnets around a plastic tube used as a barrel, and turning each of the magnets on and then off in quick succesion to propell the nail/ball bareing at imense speeds. this is the same theory that pete has posted above. Oh and by the way, that military gausse cannon fired a 7lb shell over 100 miles at roughly mach 1 to 2 speeds (this is breaking the sound barrier).
Jul 1, 2008 | 12:53 pm
millar wrote:
befor i forget, ill only post the schematics if someone asks as im not sure about the legality as it is a very high powered weapon. (and yes,i did spell “bearings” wrong, oops)
Jul 13, 2008 | 7:52 pm
RIK wrote:
Where can I get the ball bearings
Jul 13, 2008 | 7:54 pm
RIK wrote:
sorry for the double post
@millar
could you post the schematics for the cannon
Jul 13, 2008 | 7:59 pm
RIK wrote:
sorry about this,
but also where can I get a track